Polychlorinated-dibenzo-p-dioxins, -dibenzofurans and -dioxin-like polychlorinated biphenyls in aquatic organisms from lake Kasumigaura,Japan

Polychlorinated-dibenzo-p-dioxins (PCDDs), -dibenzofurans (PCDFs) and -dioxin-like polychlorinated biphenyls (DLPCBs) were determined in aquatic wildlife of Kasumigaura Lake (KUL), Japan from 1978 to 2001. Two plankton species elucidated several fold greater concentrations (2400–7800) than small tiger fish (310–6500), shrimp (160–1100), and three large fish namely, black bass (120–240), carp (94–120) and mullet (54) on pg/g fat. PCDD homologues were predominant accumulants with >68–<95% contribution and remaining was shared by PCDFs. Accumulation, non-ortho DLPCBs in plankton (3500–9200), shrimp (1600–8600) and small fish (2000–8800) and large fish (1300–3900) on ng/g fat basis were several orders magnitude greater than PCDD/DFs. The mono-ortho DLPCBs in large fish species were 23?000–83?000?ng/g fat and which it is accounted 94.3–95.9% the total dioxin-like PCBs accumulation. Temporal trends of PCDDs, PCDFs, non-ortho PCBs and TEQ in shrimp and small tiger fish were varied. The mullet had minimum toxic equivalency “TEQ” (14?pg?TEQ/g) followed by plankton Neomysis intermedia (25?pg?TEQ/g), small tiger fish (mean: 33, ranges 14–66?pg?TEQ/g), plankton Cyclopus vicinus (34?pg?TEQ/g), carp (mean: 35, ranges 32–38?pg?TEQ/g), shrimp (mean: 38, ranges 11–68?pg?TEQ/g) and black bass (mean: 59, ranges 38–79?pg?TEQ/g) on fat basis. In all the samples, PCDD was predominant TEQ contributor followed by PCDFs and DLPCBs. The contribution of mono-ortho DLPCBs to the total TEQ was 0.52–0.92 in large fish.     

The chronic toxicity of fenoxycarb to larvae of the grass shrimp,Palaemonetes pugio

Abstract

This study examined effects of fenoxycarb, a carbamate insecticide, on larvae of the grass shrimp, Palaemonetes pugio. In laboratory experiments, grass shrimp larvae were exposed to fenoxycarb from hatch to postlarval metamorphosis in a chronic, static renewal bio assay. LC50's ranged from 0.92 mg/L at 96 h to 0.35 mg/L at the end of the study (24 days). In assessing sublethal effects of fenoxycarb, postlarval emergence was significantly (p < 0.05) reduced in exposed grass shrimp as compared with controls, and the time to reach postlarval status was significantly (p < 0.05) increased in exposed grass shrimp. Significant differences were not found in other sublethal parameters including postlarval dry weight and intermolt duration. Analysis of fenoxycarb from spiked seawater samples showed concentrations declined by 32 to 42% after 24 h.     

Effects of T-2 toxin on histopathology,fatty acid and water distribution of shrimp (Litopenaeus vannamei) muscle

T-2 toxin (T-2), one of the naturally occurring mycotoxins, often accumulates in aquatic animals from contaminated feed. Shrimp (n?=?30 per group) were fed with different concentrations (0, 0.5, 1.5, 4.5 and 13.5?mg kg^?1) of T-2 for 20?days. Changes in histopathology, fatty acid and water distribution of shrimp muscle were analyzed. Histopathology of shrimp muscle showed dose-dependent marked degenerative and necrotic changes on exposure to dietary T-2. The T-2 significantly (P?<?0.05) affected the muscle fatty acid composition. ∑SFA, ∑MUFA and ∑PUFA initially decreased and then increased slowly in the high-dosed groups. C16:0, C18:1n-9 and C18:2n-6 were the main saturated fatty acid (SFA), monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA), respectively. Also, T-2 significantly affected water distribution in shrimp muscle. High doses of T-2 reduced free water content, resulting in a reduction in the water holding capacity and hence changes to the shrimp muscle quality. Collectively, these results illustrated that T-2 significantly affects the fatty acid and water distribution, and also muscle histopathology, all of which would result in a reduction in the quality and nutritional value of shrimp.     

Sludge-grown algae for culturing aquatic organisms: Part II. Sludge-grown algae as feeds for aquatic organisms

This project investigated the feasibility of using sewage sludge to culture microalgae (Chlorella-HKBU) and their subsequent usage as feeds for rearing different organisms. Part II of the project evaluated the results of applying the sludge-grown algae to feedOreochromis mossambicus (fish),Macrobrachium hainenese (shrimp), andMoina macrocopa (cladocera). In general, the yields of the cultivated organisms were unsatisfactory when they were fed the sludge-grown algae directly. The body weights ofO. mossambicus andM. macrocopa dropped 21% and 37%, respectively, although there was a slight increase (4.4%) inM. hainenese. However, when feeding the algal-fed cladocerans to fish and shrimp, the body weights of the fish and shrimp were increased 7% and 11% accordingly. Protein contents of the cultivated organisms were comparable to the control diet, although they contained a rather high amount of heavy metals. When comparing absolute heavy metal contents in the cultivated organisms, the following order was observed: alga > cladocera > shrimp, fish > sludge extracts. Bioelimination of heavy metals may account for the decreasing heavy metal concentrations in higher trophic organisms.     

Mangrove mapping in Ecuador: The impact of shrimp pond construction

A cooperative mangrove mapping project between the Ecuadorian Center for Remote Sensing (CLIRSEN) and the University of Delaware was begun in August 1982. The objectives of the project were to create historical maps of mangrove ecosystem extent and change, while transferring aerial photographic interpretation techniques to Ecuadorian personnel. The result of this cooperation was a series of three 125,000 scale maps of historical mangrove extent and change from 1966 to 1982 in the southern Gulf of Guayaquil. This multitemporal study showed a 16% decrease in mangrove extent and a 27% increase in shrimp pond development. If these rates of change prevail into the future, mangroves in Ecuador will reach parity with shrimp ponds in 1984 and completely disappear by mid-1990. Recognizing the significance of this loss to shellfish and fish production along the coast, Ecuadorian scientists at CLIRSEN have subsequently initiated a nationwide mangrove mapping program to create a historical base for future mangrove management strategies.     

An approach and preliminary model of integrating ecological and economic constraints of environmental quality in the Guayas River estuary, Ecuador

We describe conceptual and simulation models of land use within the intertidal zone of the Guayas River estuary to quantify the contribution of mangrove wetlands to maintaining environmental quality of a tropical estuary. The goal of this exercise is to demonstrate the important consideration of ecological constraints in determining economic and management decisions; and how modeling can be used to quantify impacts of land use such as loss of mangrove wetlands on environmental quality. Our conceptual model treats solar energy, river flow, and tides as forcing functions that control the properties of estuarine ecosystems, but also describes market forces and cultural policies as constraints on properties of socioeconomic systems. The controversy of coastal resource management in Ecuador centers around the relative impacts of shrimp pond construction and management as negative feedbacks to the environmental quality of the Guayas River estuary. Unique oceanographic processes and land use changes contribute to complex issues of water and habitat quality in this tropical estuary, the largest estuarine complex on the Pacific coast of South America. A dynamic box model was developed for the estuary and calibrated with data collected from a 14 month survey of water quality parameters throughout the estuary. Scenarios included conversion of mangroves to shrimp ponds in three regions of the estuary, and the construction of a dam by varying three different rates of river discharge at 100, 50 and 10% of 1989 base flow. Good water quality is maintained by the low residence time of water in the estuary (11 d) because of seasonally high river flow and tidal exchange. With a 90% reduction of mangrove forests in the estuary caused by shrimp pond construction, total nitrogen concentrations increased 5 fold. However, as river discharge decreased to 10%, the same construction caused a 60 fold increase in nitrogen concentrations to 250 μM. Increases in nitrogen concentrations were higher in the upper estuary region, with much less change in the lower estuary. Thus the sensitivity of environmental quality to changes in land use in the intertidal and upland zone are linked to the hydrography of the estuary and is site specific. In the future, the combinations of these ecological models together with economic analyses of the goods and services of mangroves may provide better techniques to evaluate the economic impacts of specific coastal zone management decisions.     

Differences in nitrite-oxidizing communities and kinetics in a brackish environment after enrichment at low and high nitrite concentrations

Nitrite accumulation in shrimp ponds can pose serious adverse effects to shrimp production and the environment.This study aims to develop an effective process for the enrichment of ready-to-use nitrite-oxidizing bacteria(NOB)inocula that would be appropriate for nitrite removal in brackish shrimp ponds.To achieve this objective,the effects of nitrite concentrations on NOB communities and nitrite oxidation kinetics in a brackish environment were investigated.Moving-bed biofilm sequencing batch reactors and continuous moving-bed biofilm reactors were used for the enrichment of NOB at various nitrite concentrations,using sediment from brackish shrimp ponds as seed inoculum.The results from NOB population analysis with quantitative polymerase chain reaction(q PCR)show that only Nitrospira were detected in the sediment from the shrimp ponds.After the enrichment,both Nitrospira and Nitrobacter coexisted in the reactors controlling effluent nitrite at 0.1 and 0.5 mg-NO_2~--N/L.On the other hand,in the reactors controlling effluent nitrite at 3,20,and 100 mg-NO_2~--N/L,Nitrobacter outcompeted Nitrospira in many orders of magnitude.The half saturation coefficients(Ks)for nitrite oxidation of the enrichments at low nitrite concentrations(0.1 and 0.5 mg-NO_2~--N/L)were in the range of 0.71–0.98 mg-NO_2~--N/L.In contrast,the Ksvalues of NOB enriched at high nitrite concentrations(3,20,and 100 mg-NO_2~--N/L)were much higher(8.36–12.20 mg-NO_2~--N/L).The results suggest that the selection of nitrite concentrations for the enrichment of NOB inocula can significantly influence NOB populations and kinetics,which could affect the effectiveness of their applications in brackish shrimp ponds.     

Sound and Fury Signifying Nothing: Using Geoinformatics to Inform Resource Policy in the Gulf of California,Mexico

In this issue of Environmental Management, Glenn and others posit that a previous study had analytical and interpretive errors in analysis of shrimp fishing in the Upper Gulf of California, Mexico. Unfortunately, much of their evidence is too indirect and of insufficient scale to address the central question of salinity in the Upper Gulf. Also, many of their suppositions did not include direct interviews with local officials or a robust understanding of remote sensing literature. This response to their rebuttal presents a set of figures and analysis demonstrating that the Colorado River flows into a closed evaporative basin known as the Laguna Salada and thus cannot flow into the Gulf of California. Readers are asked to examine the images and interpret their meaning for themselves.     

Issues,impacts, and implications of shrimp aquaculture in Thailand

Water quality impacts to and from intensive shrimp aquaculture in Thailand are substantial. Besides the surface and subsurface salinization of freshwaters, loadings of solids, oxygen-consuming organic matter, and nutrients to receiving waters are considerable when the cumulative impacts from water exchange during the growout cycle, pond drainage during harvesting, and illegal pond sediment disposal are taken into account. Although just beginning to be considered in Thailand, partial recirculating and integrated intensive farming systems are producing promising, if somewhat limited, results. By providing on-site treatment of the effluent from the shrimp growout ponds, there is less reliance on using outside water supplies, believed to be the source of the contamination.The explosion in the number of intensively operated shrimp farms has not only impacted the coastal zone of Thailand, but has also resulted in an unsustainable aquaculture industry. Abandonment of shrimp ponds due to either drastic, disease-caused collapses or more grandual, year-to-year reductions in the productivity of the pond is common. To move Thailand towards a more sustainable aquaculture industry and coastal zone environment, integrated aquaculture management is needed. Components of integrated aquaculture management are technical and institutional. The technical components involve deployment of wastewater treatment and minimal water-use systems aimed at making aquaculture operations more hydraulically closed. Before this is possible, technical and economic feasibility studies on enhanced nitrification systems and organic solids removal by oxidation between production cycles and/or the utilization of plastic pond liners need to be conducted. The integration of semi-intensive aquaculture within mangrove areas also should be investigated since mangrove losses attributable to shrimp aquaculture are estimated to be between 16 and 32% of the total mangrove area destroyed betweeen 1979 and 1993.Government policy needs to devote as much attention to sustainability issues as it has on promoting intensive pond culture. Such a balanced policy would include training and education monitoring and enforcement, rehabilitating abandoned ponds, managing land use within the coastal zone, more community involvement, and government reorganization to eliminate overlapping jurisdictions among agencies.As integrated aquaculture management becomes more the practice than the exception, less risk of crop failure to the industry and reduced discharge loadings from intensively managed shrimp ponds to receiving waters can be expected. Projected limitations on growing and marketing shrimp in the future, such as scarcity of land and broodstock, continued disease outbreaks, negative publicity, regulatory enforcement, water treatment and solids disposal costs, and increased competition from growers in other Asian countries will also drive the government and the industry towards adopting integrated aquaculture management.The data for this paper was obtained while the senior author was a Visiting Fulbright Researcher at the Coastal Resources Institute (CORIN), Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand.     

Ecological limitations and appropriation of ecosystem support by shrimp farming in Colombia

Shrimp farming in mangrove areas has grown dramatically in Asia and Latin America over the past decade. As a result, demand for resources required for farming, such as feed, seed, and clean water, has increased substantially. This study focuses on semiintensive shrimp culture as practiced on the Caribbean coast of Colombia. We estimated the spatial ecosystem support that is required to produce the food inputs, nursery areas, and clean water to the shrimp farms, as well as to process wastes. We also made an estimate of the natural and human-made resources necessary to run a typical semiintensive shrimp farm. The results show that a semiintensive shrimp farm needs a spatial ecosystem support—the ecological footprint—that is 35–190 times larger than the surface area of the farm. A typical such shrimp farm appropriates about 295 J of ecological work for each joule of edible shrimp protein produced. The corresponding figure for industrial energy is 40:1. More than 80% of the ecological primary production required to feed the shrimps is derived from external ecosystems. In 1990 an area of 874–2300 km² of mangrove was required to supply shrimp postlarvae to the farms in Colombia, corresponding to a total area equivalent to about 20–50% of the country’s total mangrove area. The results were compared with similar estimates for other food production systems, particularly aquacultural ones. The comparison indicates that shrimp farming ranks as one of the most resource-intensive food production systems, characterizing it as an ecologically unsustainable throughput system. Based on the results, we discuss local, national, and regional appropriation of ecological support by the semiintensive shrimp farms. Suggestions are made for how shrimp farming could be transformed into a food production system that is less environmentally degrading and less dependent on external support areas.